Electronic switch



Jan. 3, 1950 B. P. WASHBURNE ET AL 2,493,706

ELECTRONIC SWITCH Filed March 30, 1948 3 Sheets-Sheet l Imventor BRENTON P WASHBURNE m JAMES A. EYSTER Jan. 3, 1950 B. P. WASHBURNE ETAL ELECTRONIC SWITCH Filed March 50, 1948 5 Sheets-Sheet 2 Inventor BRENTON P; WASHBURNE E JAMES A. EYSTE attorney Jan. 3, 1-950 B. P. WASHBURNE ET AL 2,493,706

ELECTRONIC SWITCH Filed March 30, 1948 3 Sheets-Sheet 5 1n ventr- BRENTON P. WASHBURNE EB JAMES A. EYSTER/ 1 Patented Jan. 3, 1950 ELECTRONIC SWITCH Brenton P. Washbm'ne, Pleasantville, and James A. Eyster, Chappaqua, N. Y., assignors to General Precision Laboratory Incorporated, a corporation of New York Application March 30, I948, Serial No. 17,856

12 Claims. 1

The present invention relates to an improved method and apparatus for electronically switching and modulating microwaves.

In general the switching means heretofore available for rapidly controlling the transmission of microwaves in wave guides resided in the use of TR tubes which are actuated solely by variations in power level. Because these devices are responsive only to the power level incident thereon their application in various circuits is quite limited.

. The present invention has for its purpose the provision of a switch which is controlled by means external to the microwave circuit itself and whose frequency and duration of operation is wholly independent of the power level within the microwave circuit. This invention therefore provides a switch capable of a wide field of applications for which satisfactory equipment has not been heretofore available and one which is capable of operation at an extremely rapid rate.

Additionally the instant invention provides a mechanism where partial control as well as complete interruption of the microwave energy may be attained, thereby providing a means whereby the microwave energy may be modulated.

These purposes are accomplished by providing an arrangement so that the microwave energy may be selectively intersected by a beam of electrons, the beam being either interrupted completely or varied in intensity, whichever is desired for the particular application with which the device is used. By arranging the mechanism so that the beam of electrons is projected across the path of microwave energy in a direction parallel to the lines of electrical intensity in a wave guide operated in the TE1 modea complete or partial short circuit may be attained depending on the intensity of the electron beam. Where complete short circuit is attained the device acts as a switch selectively cutting off the transmission of microwave energy. On the other hand where partial short circuit is attained by adjusting the intensity of the electron beam a portion of the microwave energy is reflected while the remainder is transmitted thereby permitting a regulation of the amount of energy transmitted depending on the intensity of the electron beam. I

By varying the beam intensity in a suitable manner as by voice controlled means or otherwise a modulation of the microwave energy may thereby be attained.

In general the apparatus contemplated by the instant invention to accomplish these desirable functions consists of a rectangular wave guide angles thereto. Hermetically sealed diaphragms are positioned in the rectangular wave guide at each side of the intersecting section and the round wave guide itself is hermetically sealed so that the critical portion of the apparatus may be highly evacuated. The diaphragms inserted in the rectangular wave guide are provided with windows of glass, plastic or some other substance which is permeable to microwaves but which may be satisfactorily sealed to the metal of the diaphragms and the dimensions are made such that the microwave energy traveling along the wave guide is not impeded.

The round wave guide is pro, ded with an electron gun assembly at one end at one side of its intersection with the rectangular wave guide and intersected by a round wave guide placed at right with a collecting electrode or anode at the other so that when a beam of electrons is projected from the gun assembly to the collecting electrode the beam intersects the path of the microwave energy.

In order that there shall be no impediment to the flow of microwave energy in the rectangular wave guide when a beam of electrons is not projected thereacross matching means is utilized consisting of diaphragms having apertures of any desired shape for the admission of the electron beam are placed in the round wave guide on each side of the rectangular wave guide and at such distances therefrom that with no electron beam present the microwave energy flows through the rectangular wave guide as though it were a simple wave guide having continuous solid walls.

As heretofore stated, when a beam of electrons is projected across the rectangular wave guide the transmission of microwave energy therein is prevented or partially impeded depending on the intensity of the beam of electrons. The present invention contemplates several modes of impeding this beam of electrons to provide on-ofi switching action or of varying its intensity to modulate the microwave energy.

In one form of the invention the potential applied to the collecting electrode or anode is interrupted or varied thus controlling the electron beam in the desired manner.

In another form of the invention a grid electrode is utilized as the beam-controlling element.

In still another form of the invention deflecting means such as deflecting coils or electrostatic plates are placed adjacent the electron gun assembly and utilized to deflect the electron beam. Such a deflection of the electron beam acting in conjunction with the apertures in the matching diaphragms placed in the round wave 3 guide acts to cause the beam to, be projected through the apertures or to miss them or to be partially projected depending on the amount of deflection, thereby varying the intensity of the beam at the point of intersection with the rectangular wave guide.

In any or all of these forms suitable focusing elements may be associated guide.

The exact nature of the invention will be more clearly understood from the following detailed description when taken together with the accompanyins drawings in which:

Figure 1 is an illustration of one form of the invention, certain parts broken away for clarity.

Figure2isaviewsimilartoFig. 1 ofamodifled form of the invention.

Figure 3 is a similar view illustrating still another form of the invention.

Referring now to Fig. 1 a rectangular wave guide II is provided for the transmission of microwave energy which for example. may be introduced at the end 32 for transmission through the wave guide I I towards and out the end 33. A circular wave guide l2 consisting of two sections I and I intersects the rectangular wave guide I l the sections I. and 8 being rigidly and hermetically afllxed to the top and bottom walls respectively of the rectangular wave guide. As is well understood in the art the wave guides II and H are appropriately dimensioned for the wavelength of the microwave energy, that is, to be handled thereby, for example, and as an illustration only, where the wavelength of the microwave is 3.2 cm., i. e., x band waves, the internal width of the rectangular wave guide may be .9 inch and its height .4 inch while the internal diameter of the round wave guide is .875 inch.

Within the rectangular wave guide II and at each side of the intersection of the rectangular and round wave guides are positioned diaphragms l3 and I which are hermetically sealed to the walls of the rectangular wave guide H. Each of these diaphragms is provided with a window 9 and I respectively of glass, plastic or some other material permeable to microwave energy which may with t e round wave lar guide extending below the rectangular guide II is provided with an electron gun assembly It consisting of a heater l1 energized by a source of current here illustrated as a battery 36 for convenience and a cathode l8 which constitutes a source of electrons. If desired focusing electrodes may also be included as illustrated at 9| and 92 of Fig. 2.

The opposite end I of the circular wave guide I2 is provided with a collecting electrode or anode l9 and a power circuit is provided which may be traced from anode l9 through insulating terminal 2i, element 22, the positive pole of a potential source 24 here illustrated for the purposes of simplicity as a battery 24 to the cathode l8. Assuming that a circuit is established through element 22 there is a difference of potential existing between the cathode I8 and anode l9 which will cause a beam of electrons to be projected'from the cathode to the anode and hence across the space of the intersecting rectangular wave guide I I. As stated heretofore, if the intensity of this beam is made sufllcient by applying a suflicient potential to the anode Is the electron beam acts as a low impedance circuit placed across the microwave path and the microwave energy is reflected and not transmitted past the intersecting area. At lower anode potentials and hence lower beam intensities the impedance shunt produced by the electron beam is such that a portion of the microwave energy is reflected while another portion is transmitted.

By regulation of the intensity of the electron beam therefore, the amount of microwave energy transmitted through the wave guide ll may be regulated from a maximum to an irreducible minimum such as for example, would be transmitted even by a fired TR. tube. It is apparent therefore, that the device may be operated as a switch wherein all or practically none of the energy is transmitted or by variable regulation as a device which will transmit variable amounts of energy at the will of the user.

This control may be achieved by element 22 5 which may be a mechanical switch or an electronbe hermetically sealed to the diaphragm by which it is carried. These diaphragms with their cooperating windows permit a hermetic seal of the central and intersected portion of the wave guide It so that it may be evacuated and also serve to I source 24 and the anode l9.

When circuit is made potential will be supplied to the anode l9 causing the beam of electrons to neutralize the eflect of the discontinuity in the rectangular guide I I caused by the intersection of the circular wave guide l2. The windows are properly proportioned in size as is well understood in the art and where it is desired that the wave guide ll transmit a range of frequencies, that is, that it be a broad band guide the diaphragms are placed an odd number of quarter wavelen ths apart.

On the other hand where variation in frequency of the microwaves impressed on the wave guide I l is not expected to be great the structure may be made narrow band by placing the diaphragm l3 and it any number of half wavelengths apart.

Under these circumstances the portion of the wave guide ll included between the diaphragms l3 and Il acts as a resonant cavity having standing waves and if the electron beam is made to intersect the standing waves at a voltage maximum point the efliciency of the device is improved.

'I'o complete the hermetic seal of the area of intersection between the circular and rectangular wave guides, the ends of the circular guide I! are traverse the path across the wave guide I I blocking the transmission of. microwave energy therethrough and conversely when the circuit is broken at 22 no potential is impressed on the anode I 9,

no beam of electrons traverses the path of the wave guide II and energy is transmitted thereby.

On the other hand, the element 22 may be constituted by any variable type of control, the particular form of which forms no part of this ingo vention, which may impress a varying potential on the anode l9 producing a variable intensity in the electron beam and hence a variable transmission of microwave energy.

In order that during those periods when no 68 electron beam traverses the path of the wave guide II a maximum amount of energy be transmitted therethrough the juncture of the circular wave guide l2 and rectangular wave guide II is matched by placing diaphragms 20 and 25 in the 70 circular wave guide l2 above and below the intersection. These diaphragms are placed a half wavelength above and below the rectangular guide so as to reflect low impedance thereto. When so placed and no electron beam traverses hermetically sealed. The portion 8 of the circu-l the path of intersection transmission will be had by the wave guides II and I2.

. through the rectangular wave guide as though the circular wave guide were not present.

To permit transmission of the electron beam across the intersection of the circular wave guide I2 and the rectangular wave guide II the diaphragms and are provided with apertures and respectively and these apertures may be made of any desired shape, that is, circular as shown or as slits or slots to provide an electron beam extending across the width of the wave guide II and so forth. .These apertures if not too large will have very little eil'ect on the low impedance reflection of the diaphragms to the rectangular wave guide II but to insure such low impedance reflection the distance from each diaphragm to the end of the circular wave guide nearest thereto may also be made a half wavelength or multiple thereof. Then the closed ends of the circular wave guide reflect their low impedance to the diaphragms and from there to the rectangular guide; thus nullifying any possible eflects which might result from the use of apertures.

In Fig. 2 a modified form of the invention is disclosed which utilizes similar intersecting wave guide structure, sealing and impedance-reflecting diaphragms, a detailed description of which need not be repeated. In the device of this figure various means which may be used singly or collectively to focus and concentrate the electron beam are disclosed and while these elements may be used with any of the arrangements of the invention, they are here disclosed in connection with but one modification thereof for the purmay be passed through the aperture 40 in the diaphragm 20 to be utilized in the area intersected The lower cylinder 92 may have its bottom end closed except for a smallcenter hole to producean additional focusing eflect. As an additional or separately usable focusing device, a coil 93 may be wound about the cylindrical wave guide I2 and supplied with current from a source here represented for convenience as a battery 94. The magnetic field produced by this coil causes the electrons emitted by the cathode I8 to take spiral paths which will periodically cross each other providing an electron beam having nodes and antinodes in the manner of a vibrating string. By proper positioning and proper potentials the nodal points the electron beam, either interrupting it completely or varying its intensity, a control grid I02 is interposed between the cathode I0 and electrostatic focusing electrodes 9I and 02. A circuit is established between the grid I02 and cathode I0 consisting of a potential varying device I03 and potential source, for convenience ill trated as a battery I04. The potential vary device I03 may be any one of many well-known devices depending on the use to which the device may be put. It may for example, be a simple mechanical switch which when actuated places such a negative potential on the grid I02 as to interrupt the electron beam and when not actuated places the grid at a potential which permits the passage of the electron beam. Additionally the device I03 may be constituted by a square wave generator or a pulse generator which applies such a negative potential to the grid as to interrupt the electron beam and where a pulse generator'is used the action may be extremely rapid in the order of a micro-second or so. In these instances the device will act merely as an on-off switch for the microwave energy albeit the action may be extremely rapid as indicated.

When it is desired to modulate the microwave energy a variable potential may be applied to the grid I02 by means of a microphone and amplifier circuit as is customary in ordinary discharge tube circuits, in this case of course, the circuit element I03 would consist of a suitable microphone and amplifier circuit or other grid potential varying means. By varying the grid potential in this manner the intensity of the electron beam will be varied over a range of intensities rather than absolutely interrupted as by switch action and concomitant therewith the transmission of microwave energy through the wave guide II is also varied over a range producing a modulation effect.

Referring now to Fig. 3 still another modification of the invention is disclosed which while using similar intersecting wave guide structure, sealing and impedance-reflecting diaphragms, a repetition of description of whichis unnecessary, incorporates a different means for switching and/or modulating the electron beam and hence the transmission of microwave energy.

In the disclosure of this figure the representation of the potential supply sources for the cathode, heater and anode have been omitted for the sake of clarity. Adjacent portion 8 of the wave guide I2 and positioned at a point intermediate -the cathode I8 and diaphragm 20 are located of the electron beam may be made to occur at i This action is illustrated generally by dotted lines 0| and 02.

As the means for controlling the intensity of coils I06 and I071. These coils are energized by a current source indicated diagrammatically by a battery I08 through a circuit which includes the device I09. The device I09 may be as aforesaid, a mechanical or electronic switching device which will interrupt the power supplied to coils I06 and I0? or may be a current varying device as a microphone and the like.

Assuming, in the first instance, that the device I09 is a simple switching device that either connects or disconnects the power supply I08 to the coils I06 and I01, then when no power is applied to these coils no magnetic field is generated thereby and the electron beam is projected from the cathode I8 to the anode I9 through the aperture 40 in the diaphragm 20, the aperture 40 being in axial alignment with the cathode I8 and anode I9.

If now, through action of the switch I09 a current from the source I08 is allowed to flow through thecoils I06 and I01 a magnetic field will be generated thereby which will cause the electron beam to be deflected to one side or the to such an extent that none of it will pass through the aperture "and hence will not be projected across the wave guide I I to interrupt the flow of microwave energy therein.

when, however, a current varying device is inserted at I09 in circuit with coils m and m and the source I08 the strength or the magnetic field developed by the coils I08 and I 01 may be varied and hence the amount of deflection or the electron beam also varied. When the electron beam is deflected a small amount, part of this beam will enter the aperture ll and so be projected across the wave guide ll while another part thereof will strike the diaphragm 2| and will not be so projected. By appropriately varying the deflection of the electron beam the portion which is allowed to pass through the aperture 40 may be varied a desired amount and hence the intensity of that portion of the beam which is projected across the wave guide II and is instrumental in controlling the transmission of microwave energy therethrough is varied in a like manner. Inasmuch as it is the intensity of the electron beam at the intersecting area of the wave guides which determines the amount of microwave energy which will be transmitted modulation of this energy may be obtained in this manner.

The same results of deflectin the electron beam and obtaining switching action or modulation as described may likewise be procured by the use of suitably energized electrostatic deflection plates in place of the magnetic deflection coils I06 and I01.

While'in the above description a rectangular guide has been referred to as used for the transmission or microwave energy and a circular guide referred to as the electron beam generating and transmitting means it will be appreciated that other shapes may be used without departing from the spirit and scope of this invention, these particular forms and shapes being merely preferred for ease in design.

What is claimed is:

1. A device of the character described comprising, a first wave guide for the transmission of microwave energy therethrough, a second wave guide intersecting said first wave guide and extending in a direction parallel to the lines of electric intensity of the microwave energy introduced in said first wave guide, means for generating a beam of electrons in said second wave guide section, means for selectively projecting said beam of electrons across said first wave guide in a direction parallel to the lines of electric intensity of the microwave energy introduced therein and means for maintaining a vacuum in said second wave guide and the portion of said first wave guide intersected thereby.

2. A device according to claim 1 in which said means for maintaining a vacuum in said second wave guide and the intersected portion of said first waveguide includes a first diaphragm havr 8 onesideoithepointot intersection otsaidfirst v and second wave guides, and a second diaphragm having a window permeable to microwave energy hermetically sealed in said first wave guide at the opposite side of the point of intersection of said first and second wave guides, the distance between said diaphragms being an odd number of quarter wavelengths.

3. A device according to claim 1 in which said 10 means for maintaining 'a vacuum in said second wave guide and the intersected portion of said first wave guide includes a first diaphragm having a window permeable to microwave energy hermetically sealed in said first wave guide at one side of the point of intersection of said first and second wave guides, and a second diaphragm having a window permeable to microwave energy hermetically sealed in said first wave guide at the opposite side of the point of intersection -of said first and second wave guides. the distance between said diaphragms being a multiple of half wavelengths.

4. A device of the character described comprising a first wave guide for the transmission of microwave energy therethrough, a second wave guide intersecting said firstgwave guide and extending in a direction parallel to the lines of electric intensity of the microwave energy introduced in said first wave guide, diaphragms permeable to microwave energy inserted in said first wave guide on either side of the intersection of said first wave guide by said second wave guide hermetically sealing said second wave guide and the intersected portion of said first wave guide, a cathode in said second wave guide located at one side of the intersection of said first and second wave guides, an anode located in said second wave guide at the opposite side of said intersection of said first and second wave guides, diaphragms having apertures therein located in said second wave guide at each side of the intersection of said first and second wave guides at distances of a half wavelength from said first wave guide and means for variably projecting a beam of electrons from said cathode to said anode across said first wave guide.

5. A device according to claim 4 in which said means for variably projecting a beam of electrons from said cathode to said anode comprises a switch connected in circuit with said anode and a power source therefor.

6. A device according to claim 4 in which said means for variably projecting a beam of electrons from said cathode to said anode comprises a grid electrode interposed between the cathode and anode and a circuit connected between said grid electrode and said cathode including means for impressing a variable potential on said grid electrode.

7. A device according to claim 4 in which said means for variably projecting a beam of electrons from said cathode to said anode comprises 55 deflecting members located at opposite sides of said electron beam between said cathode and the diaphragm positioned on the cathode side of the intersection of saidfirst and second wave guides, said deflecting members being variably energized whereby the electron beam may be bent toward and away from the aperture in said diaphragm.

'8. A device according to claim 4 in which said means for variably projecting a beam of electrons from said cathode to said anode comprises deflecting coils located at opposite sides or said electron beam between said cathode and the diaphragm positioned on the cathode side of the intersection of said first and second wave guides, said deflecting coils being variably energized whereby the electron beam may be bent toward and away from the aperture in said diaphragm.

9. A device of the character described comprising a first wave guide for the transmission of microwave energy therethrough, a second wave guide intersecting said first wave guide and extending in a direction parallel to the lines of electric intensity of the microwave energy introduced in said first wave guide, diaphragms permeable to microwave energy inserted in said first wave guide on either side of the intersection of said first wave guide by said second wave guide hermetically sealing said second wave guide and the intersected portion of said first wave guide, a cathode in said second wave guide located at one side of the intersection of said first and second wave guides, an anode located in said second wave guide at the opposite side of said intersection of said first and second wave guides, diaphragms having apertures therein located in said second wave guide at eachside of said intersection of said first and second wave guides at distances a half wavelength from said first wave guide,'means for variably projecting a beam of electrons from said cathode to said anode across said first wave guide and means for focusing said beam of electrons for passing a substantial portion thereof through the apertures in the diaphragms located in said second wave guide.

10. A device according to claim 9 in which the means for focusing said beam of electrons includes at least one cylindrical electrode having applied thereto a potential which is positive with respect to the potential of the cathode.

11. A device according to claim 9 in which the means for focusing said beam of electrons includes a coil arranged axially with respect to said second wave guide which is supplied with a current such that the electrons emitted by the cathode are caused to follow a spiral path producing a beam having nodes and antinodes, the nodes occurring at the positions occupied by the apertures in the diaphragms located in said second wave guide.

12. A device according to claim 9 in which the means for focusing said beam of electrons includes a coil arranged axially with respect to said second wave guide which is supplied with a current such that the electrons emitted by the cathode are caused to follow a spiral path producing a beam having nodes and antinodes, the nodes occurring at the positions occupied by the apertures in the diaphragms located in said second wave guide and at least one cylindrical electrode having applied thereto a potential which is positive with respect to the potential of the cathode.

BRENTON P. WASHBURNE. JAMES A. EYSTER.

REFERENCES CITED The following references are of record in the file of this patent:

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